Diaphragm pump

ABSTRACT

A diaphragm pump includes: a volume changing member which changes the volume of a fluid chamber; a diaphragm member fixed in a stretched state and arranged separate from the fluid chamber, the diaphragm member having a pair of electrodes and a stretch film formed of dielectric elastomer, and the diaphragm member driving the volume changing member in a forward movement direction; a return bias member which drives the volume changing member in a backward movement direction; and a connection member which connects the diaphragm member and the volume changing member. In a low voltage state, the diaphragm member and the return bias member have driving force with respect to the volume changing member. The diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to that in the stretched state is set to 45° or greater in a cross section along a reciprocal movement direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2007-224382 filed on Aug. 30, 2007 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a diaphragm pump which pumps a fluid using an electrostrictive diaphragm member.

2. Description of the Related Art

For example, FIG. 2H of Published Japanese Translation of PCT Application No. 2003-506858, FIG. 2G of Published Japanese Translation of PCT Application No. 2005-522162, FIG. 6 of Japanese Patent Application Publication No. JP-A-2001-286162, and FIGS. 8C, 8D, and 8E of Published Japanese Translation of PCT Application No. 2006-520180 disclose a diaphragm actuator or pump. The actuator or pump includes a diaphragm member having stretch films formed of dielectric elastomer.

SUMMARY OF THE INVENTION

FIGS. 1A to 1C show operation principle diagrams of a diaphragm member. FIG 1A shows the diaphragm member in a state where voltage is not applied. FIG. 1B shows the diaphragm member in a state where voltage is applied without restricting deformation in a film expansion direction. FIG. 1C shows the diaphragm member in a state where voltage is applied with the deformation being restricted in the film expansion direction.

As shown in FIG. 1A, a diaphragm member 100 includes a stretch film 101, and a pair of electrodes 102 a and 102 b. As shown in FIG. 1B, closing a switch 103 causes a voltage to be applied between the electrodes 102 a and 102 b. When the voltage is applied, an electrostatic attractive force between the electrodes 102 a and 102 b increases. Therefore, the stretch film 101 is compressed in a film thickness direction, whereby a film thickness of the stretch film 101 decreases. When the film thickness decreases, the stretch film 101 correspondingly extends in the film expansion direction.

However, as shown in FIG. 1C, in the case where the periphery of the stretch film 101 is fixed, the stretch film 101 cannot extend in the film expansion direction. Therefore, the stretch film 101 bends in a substantially perpendicular direction with respect to the film expansion direction. In the case of the diaphragm actuator or pump disclosed in Published Japanese Translation of PCT Application No. 2003-506858, Published Japanese Translation of PCT Application No. 2005-522162, Japanese Patent Application Publication No. JP-A-2001-286162, and Published Japanese Translation of PCT Application No. 2006-520180, an amount of the bend is used to ensure a stroke L1.

In the case of the diaphragm actuator or pump disclosed in Published Japanese Translation of PCT Application No. 2003-506858, Published Japanese Translation of PCT Application No. 2005-522162, Japanese Patent Application Publication No. JP-A-2001-286162, and Published Japanese Translation of PCT Application No. 2006-520180, the stroke L1 is ensured in the substantially perpendicular direction with respect to the film expansion direction. In other words, the stroke L1 is ensured in the substantially perpendicular direction with respect to an original stretch direction of the stretch film 101. Therefore, the stroke tends to be small.

A diaphragm pump of the present invention has been completed in view of the problem described above. Thus, an object of the present invention is to provide a diaphragm pump in which a large stroke can easily be ensured.

(1) In order to solve the problem described above, a diaphragm pump (hereinafter appropriately referred to simply as “pump”) according to one aspect of the present invention includes: a housing member including a fluid chamber, a suction opening which sucks a fluid into the fluid chamber, and a discharge opening which discharges the fluid from the fluid chamber, a volume changing member which changes a volume of the fluid chamber; a diaphragm member which is fixed to the housing member in a stretched state where a periphery of the diaphragm member is extended in a radial direction, and which is arranged separate from the fluid chamber, the diaphragm member including a pair of electrodes and a stretch film formed of dielectric elastomer, which is provided between the pair of electrodes and an extension amount of which increases in a film expansion direction as an applied voltage between the pair of electrodes increases, and the diaphragm member driving the volume changing member in a forward movement direction which intersects with the film expansion direction; a return bias member which drives the volume changing member in a backward movement direction opposite to the forward movement direction; and a connection member which connects the diaphragm member and the volume changing member so as to be capable of power transmission. In the diaphragm pump, a low voltage state where the applied voltage between the pair of electrodes is low and a high voltage state where the applied voltage between the pair of electrodes is high can be switched. In the low voltage state, the diaphragm member and the return bias member have an accumulated driving force with respect to the volume changing member, the diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to the diaphragm member in the stretched state is set to 45° or greater in a cross section along a reciprocal movement direction. The “low voltage state” used herein includes a state where no voltage is applied between the pair of electrodes (state where the applied voltage is 0V).

In the pump of the present invention, the stretch film of the diaphragm member is stretched in advance. When the stretch film, i.e., a dielectric elastomer, is used in a state where the stretch film is stretched in advance, dielectric breakdown strength is improved compared to a case where the dielectric elastomer is used in an unstretched state. Therefore, with the pump of the present invention, larger voltage can be applied to the stretch film. Thus, a stroke of the pump can be increased.

The stretch film of the diaphragm member is stretched in the radial direction (outer radial direction). Presence and absence of the stretch in the radial direction will be described below using model diagrams. Note that the model diagrams discussed below are for illustrating an advantageous effect of the stretch in the radial direction. The model diagrams discussed below do not in any way limit the shape of the stretch film, the shape of the connection member, arrangement, and the like of the pump of the present invention.

FIGS. 2A and 2B are model diagrams showing the direction of force of the stretch film in two different stretch states. FIG. 2A shows the stretch film that is fixed while being stretched in the radial direction. FIG. 2B shows the stretch film fixed in a natural state without being stretched in the radial direction. In both states of FIGS. 2A and 2B, a central section of the stretch film is pressed by the connection member. In FIGS. 2A and 2B, the direction of force is shown by an arrow. As shown in FIG. 2A, in the case where a stretch film 104 is stretched in the radial direction, a tensile force occurs uniformly from the center toward the periphery of the stretch film 104. As shown in an enlarged view in a dotted-line circle in FIG. 2A, the tensile force occurs in the radial direction (outward). Therefore, the respective forces hardly interfere with each other. Thus, the advantageous effect of the stretch can sufficiently be obtained throughout the entire stretch film 104. On the other hand, as shown in FIG. 2B, in the case where the stretch film 104 is not stretched in the radial direction, the tensile force occurs from the periphery toward the center of the stretch film 104 due to the central section of the stretch film 104 being pressed by the connection member. As shown in an enlarged view in a dotted-line circle in FIG. 2B, the tensile force occurs in the central direction (inward). Therefore, the respective forces overlap and easily interfere with each other. Therefore, a twist, wrinkle, or the like easily occurs in the stretch film 104, whereby the advantageous effect of the stretch of the stretch film 104 cannot be sufficiently obtained.

In the pump of the present invention, the stretch film is fixed to the housing member in the stretched state. Therefore, the advantageous effect of the stretch can be sufficiently achieved. Thus, the dielectric breakdown strength of the stretch film is high. Also, it suffices that the stretch film be stretched in the radial direction and fixed when the pump is assembled. Therefore, it is not necessary to subject the stretch film to a stretching process in advance before assembling the pump. Therefore, assembly of the pump is easy.

The diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state. In addition, the inclination angle of the diaphragm member in the low voltage state with respect to that in the stretched state is set to 45° or greater in a cross section along the reciprocal movement direction. Therefore, a stretch direction (film expansion direction) of the stretch film and the reciprocal movement direction (stroke direction) intersect at an angle of less than 45°. Thus, the stroke of the pump can be increased in this regard as well.

In the pump of the present invention, the diaphragm member is separated from the fluid chamber. Therefore, there is a small chance of the fluid contacting the diaphragm member. Thus, there is a small chance of the diaphragm member being degraded by the fluid. Since the diaphragm member is separated from the fluid chamber, the fluid can be selected without taking the material of the diaphragm member into consideration. Thus, the fluid can be selected from a wide variety of choices. In addition, the material of the diaphragm member can be selected from a wide variety of choices.

In the pump of the present invention, the volume changing member is driven in the forward movement direction by the diaphragm member during a forward movement. In addition, the volume changing member is driven in the backward movement direction by the return bias member during a backward movement. That is, the volume changing member is driven in both forward and backward directions by the diaphragm member (during the forward movement) and the return bias member (during the backward movement). Therefore, the operation of the volume changing member is fast compared to a case where the volume changing member is driven only by the diaphragm member. Thus, it is easy to change the volume of the fluid chamber, and a flow rate of the fluid per unit time can be increased.

(2) In the configuration of (1) described above, the pump preferably has a configuration in which the volume changing member is a rubber elastic member. In the pump of this configuration, by using the elastic deformation of the rubber elastic member, the volume of the fluid chamber can be changed relatively easily and at low cost.

(3) In the configuration of (2) described above, the pump preferably has a configuration in which the rubber elastic member also serves as the return bias member. That is, in the pump of this configuration, the rubber elastic member drives itself in the backward movement direction opposite to the forward movement direction by using elastic resilience inherent to the rubber elastic member. In the pump of this configuration, the number of parts can be reduced compared to a case where the rubber elastic member and the return bias member are respectively arranged individually.

(4) In the configuration of (2) described above, the pump preferably has a configuration in which a static spring constant of the rubber elastic member is set to be greater than or equal to a static spring constant of the diaphragm member.

In the case of the pump of the present invention, a surface area of the diaphragm member tends to be greater than that of the rubber elastic member due to dimensional limitations. In the pump of this configuration, since the static spring constant of the rubber elastic member is set to be greater than the static spring constant of the diaphragm member, the length of the fluid chamber in the reciprocal movement direction can be shortened.

(4-1) In the configuration of (2) described above, it is particularly preferable that the pump has a configuration in which the static spring constant of the rubber elastic member and the static spring constant of the diaphragm member are set to be equal. Accordingly, although the length of the fluid chamber in the reciprocal movement direction increases, the stroke can be increased.

(5) In the configuration of (1) described above, the pump preferably further includes a piston member including a piston body which serves as the volume changing member and a rod section which serves as the connection member connected with the piston body.

In the pump of this configuration, the volume of the fluid chamber is changed by the piston body having high rigidity. Therefore, there is a smaller chance of the member itself (the piston body itself) being deformed compared to a case where the volume of the fluid chamber is changed by a soft member having low rigidity. Therefore, the volume can easily be changed.

(6) In the configuration of (1) described above, the pump preferably has a configuration in which the connection member includes a substantially spherical surface-shaped spherical surface section contacting the diaphragm member. In the pump of this configuration, load is transmitted to the connection member from the diaphragm member via the spherical surface section. Therefore, the loss of the load is small. Also, the load can be transmitted smoothly.

(7) In the configuration of (6) described above, the pump preferably has a configuration in which the connection member includes a substantially sphere-shaped sphere member which includes the spherical surface section, and a concave member which contacts the volume changing member and includes a concave section accommodating a part of the sphere member.

In the pump of this configuration, the load from the diaphragm member is transmitted to the volume changing member via the sphere member and the concave member. Therefore, the loss of the load is small even when a direction of load transmission from the diaphragm member to the sphere member and the forward movement direction of the volume changing member do not coincide. Also, the load can be transmitted smoothly.

(8) In the configuration of (7) described above, the pump preferably has a configuration in which an accommodating surface of the concave section has a triangular pyramid mold shape which fits a surface of a triangular pyramid so that the sphere member comes into contact with the accommodating surface of the concave section at three points. In the pump of this configuration, the concave section and the sphere member are in contact at only three points. Therefore, a sliding resistance in the case where the concave section and the sphere member relatively slide can be reduced.

(9) In the configuration of (1) described above, the pump preferably has a configuration in which at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of a low friction material. In the pump of this configuration, a sliding resistance in the case where the connection member and the diaphragm member relatively slide can be reduced.

(10) In the configuration of (1) described above, the pump preferably has a configuration in which at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of an insulating material. In the pump of this configuration, insulation can be ensured between the diaphragm member and the connection member even in the case where voltage is applied between the pair of electrodes of the diaphragm member.

(11) In the configuration of (1) described above, the pump preferably has a configuration in which a surface of the diaphragm member on a side of the fluid chamber is formed of an insulating material. In the pump of this configuration, even if conductive fluid leaks from the fluid chamber, a short circuit of the pair of electrodes of the diaphragm member by conductive fluid can be controlled.

(12) In the configuration of (1) described above, the pump preferably has a configuration in which the diaphragm member is formed of a plurality of the stretch films being laminated with the electrode interposed therebetween.

In the pump of this configuration, the diaphragm member has a laminated structure in which the plurality of stretch films and the electrodes are alternately laminated. Therefore, since the stretch films are laminated, a larger load can be generated correspondingly.

(13) In the configuration of (1) described above, the pump preferably has a configuration in which the electrode is capable of stretching so as not to restrict stretching of the stretch film.

If the electrode restricts the stretching of the stretch film, the stretch film cannot deform sufficiently, whereby it becomes harder to ensure a desired stroke. In the pump of this configuration, the electrode does not restrict the stretching of the stretch film. That is, the electrode and the stretch film deform integrally. Therefore, the desired stroke can easily be ensured.

The output of the pump is ensured by a stretching force of the diaphragm member and the biasing force of the return bias member. When the electrode restricts the stretching of the stretch film, part of the stretching force of the stretch film and the biasing force of the return bias member is consumed since the electrode is forcibly stretched together with the stretch film. Therefore, the output decreases corresponding to the consumed amount. In the pump of this configuration, the electrode is capable of stretching in accordance with the stretching of the stretch film. That is, the electrode and the stretch film can deform integrally. Therefore, the decrease of the output can be suppressed.

(14) In the configuration of (1) described above, the pump preferably has a configuration in which the dielectric elastomer is one or more selected from a group consisting of acrylic rubber, silicone rubber, fluoro-rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, styrene butadiene rubber, and natural rubber.

The type of the dielectric elastomer is not particularly limited as long as the dielectric elastomer deforms in accordance with the electrostatic attractive force between the electrodes. The acrylic rubber, silicone rubber, fluoro-rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, styrene butadiene rubber, and natural rubber in the pump of this configuration are all preferable due to high performance regarding dielectric properties and dielectric breakdown.

According to the present invention, a diaphragm pump in which a large stroke can easily be ensured can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a diaphragm member in a state where voltage is not applied;

FIG. 1B is a schematic diagram of the diaphragm member in a state where voltage is applied without restricting deformation in a film expansion direction;

FIG. 1C is a schematic diagram of the diaphragm member in a state where voltage is applied with the deformation being restricted in the film expansion direction;

FIG. 2A is a schematic diagram of a stretch film that is fixed while being stretched in a radial direction;

FIG. 2B is a schematic diagram of the stretch film fixed in a natural state without being stretched in the radial direction;

FIG. 3 is a perspective view of a pump of a first embodiment;

FIG. 4 is an exploded perspective view of the pump;

FIG. 5 is an exploded perspective view of a diaphragm member of the pump;

FIG. 6 is an axial direction sectional view of the pump in a low voltage state;

FIG. 7 is an axial direction sectional view of the pump in a high voltage state;

FIG. 8 is a perspective view of a pump of a second embodiment;

FIG. 9 is an exploded perspective view of the pump;

FIG. 10 is an axial direction sectional view of the pump in a low voltage state;

FIG. 11 is an axial direction sectional view of the pump in a high voltage state;

FIG. 12 is an axial direction sectional view of a pump of a third embodiment in a low voltage state;

FIG. 13 is an axial direction sectional view of the pump in a high voltage state;

FIG. 14 is an exploded perspective view of a pump of a fourth embodiment;

FIG. 15 is an axial direction sectional view of the pump in a low voltage state;

FIG. 16 is an axial direction sectional view of the pump in a high voltage state;

FIG. 17 is a perspective view of a pump of a fifth embodiment;

FIG. 18 is an exploded perspective view of the pump;

FIG. 19 is an axial direction sectional view of the pump in a low voltage state; and

FIG. 20 is an axial direction sectional view of the pump in a high voltage state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a diaphragm pump of the present invention used for cooling an engine control unit (ECU) of an automobile will be described below.

First Embodiment

Configuration of Diaphragm Pump

First, a configuration of the diaphragm pump of this embodiment will be described. FIG. 3 shows a perspective view of the pump of this embodiment. FIG. 4 shows an exploded perspective view of the pump. FIG. 5 shows an exploded perspective view of a diaphragm member of the pump. FIG. 6 shows an axial direction (vertical direction) sectional view of the pump in a low voltage state. FIG. 7 shows an axial direction sectional view of the pump in a high voltage state.

As shown in FIGS. 3 to 7, a pump 1 mainly includes a housing member 20, a rubber elastic member 21, a diaphragm member 22, a connection member 23, and an inner cylinder 24. As shown in FIGS. 6 and 7, the pump 1 forms a part of an ECU cooling circuit C. A cooling liquid circulates in the ECU cooling circuit C. The cooling liquid is included in a fluid of the present invention.

The housing member 20 includes an end plate 200, an outer cylinder 201, and a flange 202. The end plate 200 includes an end plate body 200 a and a suction/discharge section 200 b. The end plate body 200 a is formed of polyamide and is disk-shaped. A circle hole 200 c is formed in a central section of the end plate body 200 a. A pair of bolt holes 200 d are formed in the end plate body 200 a in opposing positions 180° away from each other with the circle hole 200 c therebetween.

The suction/discharge section 200 b is formed of polyamide and is disk-shaped. The suction/discharge section 200 b closes the circle hole 200 c from above. A suction opening 200 f and a discharge opening 200 g are formed in the suction/discharge section 200 b. A suction cylinder 200 h formed of polyamide is connected to the suction opening 200 f. In addition, a discharge cylinder 200 k formed of polyamide is connected to the discharge opening 200 g.

The outer cylinder 201 is formed of polyamide and is cylinder-shaped. The outer cylinder 201 is arranged below the end plate 200. A diaphragm fixing groove 201 a is provided around an outer circumference surface of the outer cylinder 201. Also, a pair of flange fixing concave sections 201 b are provided on the outer circumference surface of the outer cylinder 201 in positions 180° away from each other. The flange fixing concave sections 201 b are provided below the diaphragm fixing groove 201 a.

The flange 202 is formed of polyamide and is ring-shaped. A pair of convex sections 202 a are provided to protrude on an inner circumference surface of the flange 202 in positions 180° away from each other. By inserting the pair of convex sections 202 a to the flange fixing concave sections 201 b, the flange 202 is fixed to the outer circumference surface of the outer cylinder 201. A pair of bolt holes 202 b are formed in the flange 202 in positions 180° away from each other. The pair of bolt holes 200 d of the end plate 200 and the pair of bolt holes 202 b of the flange 202 face each other in the vertical direction. Cylinder-shaped spacers 202 c are respectively mounted between the pair of bolt holes 200 d and the pair of bolt holes 202 b. A pair of bolts 202 d respectively penetrate the bolt hole 200 d of the end plate 200, the spacer 202 c, and the bolt hole 202 b of the flange 202. Penetrating ends of the pair of bolts 202 d are respectively screwed to nuts 202 e. By the pair of bolts 202 d, the end plate 200 and the flange 202 are assembled.

The inner cylinder 24 is formed of polyamide and is cylinder-shaped. The inner cylinder 24 closes the circle hole 200 c of the end plate body 200 a from below. Therefore, an upper end opening of the inner cylinder 24 is sealed by the suction/discharge section 200 b. The inner cylinder 24 is arranged on an inner radial side of the outer cylinder 201.

The rubber elastic member 21 is formed of rubber and is circular film-shaped. The rubber elastic member 21 covers a lower end opening of the inner cylinder 24. A fluid chamber R is defined by being surrounded by a lower surface of the suction/discharge section 200 b, an upper surface of the rubber elastic member 21, and an inner circumference surface of the inner cylinder 24. By the deformation of the rubber elastic member 21, the volume of the fluid chamber R can be changed.

As shown in FIG. 5, the diaphragm member 22 is formed by laminating a total of six negative electrodes 220, a total of five positive electrodes 221, a total of ten stretch films 222, and one insulating film 223.

The negative electrode 220 and the positive electrode 221 are formed of rubber in which conductive carbon black is mixed, and are circular film-shaped. The negative electrode 220 and the positive electrode 221 are deformed together with the stretch film 222 so as not to restrict the stretching of the stretch film 222. The six negative electrodes 220 are bundled at one end of the diaphragm member 22 in a diameter direction. The six negative electrodes 220 are connected to a negative side of a power supply via a switch S. The five positive electrodes 221 are bundled at the other end of the diaphragm member 22 in the diameter direction. The five positive electrodes 221 are connected to a positive side of the power supply.

The stretch film 222 is formed of acrylic rubber and is circular film-shaped. The stretch film 222 has a slightly larger diameter than those of the negative electrode 220 and the positive electrode 221. The stretch film 222 is interposed between the negative electrode 220 and the positive electrode 221. That is, voltage is applied to the stretch film 222 by a pair of the negative electrode 220 and the positive electrode 221 which are adjacent in the vertical direction.

The insulating film 223 is formed of rubber and is circular film-shaped. The insulating film 223 is arranged in an uppermost section of the diaphragm member 22. That is, the insulating film 223 covers other members forming the diaphragm member 22 from above.

The diaphragm member 22 covers an upper end opening of the outer cylinder 201. The periphery of the diaphragm member 22 is fixed to the diaphragm fixing groove 201 a by a clamp ring 224 formed of steel. The diaphragm member 22 is mounted to the outer cylinder 201 in a stretched state where the periphery is extended in the radial direction.

The connection member 23 includes a sphere member 230 and a concave member 231. The connection member 23 is mounted between the diaphragm member 22 below and the rubber elastic member 21 above. The sphere member 230 is formed of polyamide and is substantially sphere-shaped. The sphere member 230 is in contact with a central section of an upper surface of the diaphragm member 22. The concave member 231 is formed of polyamide and is circular column-shaped. An upper surface of the concave member 231 is in contact with a lower surface of the rubber elastic member 21. A lower surface of the concave member 231 is provided with a concave section 231 a. The concave section 231 a accommodates an upper end section of the sphere member 230. An inner space of the concave section 231 a is triangular pyramid-shaped. That is, an accommodating surface of the concave section 231 a is triangular pyramid mold-shaped. Therefore, the sphere member 230 is in contact with the accommodating surface of the concave section 231 a at three points. By the connection member 23 being mounted between the diaphragm member 22 and the rubber elastic member 21, the central section of the diaphragm member 22 is elastically deformed in a low voltage state shown in FIG. 6, and it projects below. Therefore, the diaphragm member 22 has an upward biasing force. By the connection member 23 being mounted between the diaphragm member 22 and the rubber elastic member 21, the central section of the rubber elastic member 21 is elastically deformed in the low voltage state shown in FIG. 6, and it projects up. Therefore, the rubber elastic member 21 has a downward biasing force. As shown in FIG. 6, an inclination angle θ of the diaphragm member 22 in the low voltage state with respect to the diaphragm member 22 in the stretched state (shown by a dotted line in FIG. 6) is set to 45° or greater.

Method of Assembling Diaphragm Pump

Next, a method of assembling the diaphragm pump of this embodiment will be briefly described. For the assembly, the suction/discharge section 200 b is first joined with the end plate body 200 a. The suction/discharge section 200 b is mounted with the suction cylinder 200 h and the discharge cylinder 200 k in advance. In addition, the inner cylinder 24 is joined with the end plate body 200 a. The rubber elastic member 21 is subjected to vulcanization adhesion with the inner cylinder 24 in advance. The diaphragm member 22 is fixed to the outer cylinder 201 in the stretched state using the clamp ring 224. The flange 202 is set around the outer cylinder 201 in advance. Next, the connection member 23 is mounted between the upper surface of the diaphragm member 22 and the lower surface of the rubber elastic member 21. In addition, the spacer 202 c is mounted between a position corresponding to the bolt hole 200 d on the lower surface of the end plate body 200 a and a position corresponding to the bolt hole 202 b on the upper surface of the flange 202. Then, the bolt 202 d is penetrated from above the bolt hole 200 d to reach below the bolt hole 202 b. Then, the nut 202 e is screwed to the penetrating end (lower end) of the bolt 202 d. In this manner, the pump 1 of this embodiment is assembled.

Operation of Diaphragm Pump

Next, an operation of the diaphragm pump of this embodiment will be described. As shown in FIG. 6, the switch S is opened in the low voltage state. Therefore, voltage is not applied to the stretch film 222 of the diaphragm member 22 shown in FIG. 5. As described above, in the low voltage state, the central section of the diaphragm member 22 is elastically deformed, and it projects below. Therefore, the diaphragm member 22 has an upward biasing force. Also, in the low voltage state, the central section of the rubber elastic member 21 is elastically deformed, and it projects up. Therefore, the rubber elastic member 21 has a downward biasing force.

Closing the switch S causes the high voltage state, whereby predetermined voltage is applied between the negative electrode 220 and the positive electrode 221 shown in FIG. 5. Therefore, an electrostatic attractive force between the negative electrode 220 and the positive electrode 221 increases. Thus, the stretch film 222 is compressed in a film thickness direction, whereby a film thickness of the stretch film 222 decreases (see FIG. 1 described above). When the film thickness decreases, the stretch film 222 correspondingly extends in the film expansion direction. However, the periphery of the stretch film 222 is fixed to the diaphragm fixing groove 201 a of the outer cylinder 201. Therefore, as shown in FIG. 7, the stretch film 222 bends downward due to the biasing force of the rubber elastic member 21 and the weight of the connection member 23. In addition, the connection member 23 also descends. The rubber elastic member 21 moves back to a substantially planar state. When the rubber elastic member 21 moves back, the volume of the fluid chamber R correspondingly increases. Therefore, a suction side check valve V1 opens (a discharge side check valve V2 is closed), whereby the cooling liquid flows into the fluid chamber R from the ECU cooling circuit C via the suction cylinder 200 h and the suction opening 200 f.

When the switch S is opened again, the high voltage state is switched to the low voltage state. Therefore, as shown in FIG. 6, the diaphragm member 22 moves back upward. When the diaphragm member 22 ascends, the connection member 23 also ascends. Also, the central section of the rubber elastic member 21 is pressed by the connection member 23 to deform and protrude upward. When the central section of the rubber elastic member 21 is deformed to protrude, the volume of the fluid chamber R correspondingly decreases. Therefore, the discharge side check valve V2 opens (the suction side check valve V1 is closed), whereby the cooling liquid flows out to the ECU cooling circuit C from the fluid chamber R via the discharge opening 200 g and the discharge cylinder 200 k.

As described above, the pump 1 of this embodiment alternately causes the low voltage state and the high voltage state by repeating opening/closing of the switch S to circulate the cooling liquid in the ECU cooling circuit C. The circulating cooling liquid cools the ECU which is a heat source on the pump 1 exit side. The cooling liquid which has become high in temperature due to heat exchange with the ECU is cooled by a radiator to return to low temperature. The cooling liquid returned to low temperature flows into the pump 1, and cools the ECU again on the pump 1 exit side. In this manner, the cooling liquid circulates the ECU cooling circuit C.

Advantageous Effect

Next, an advantageous effect of the diaphragm pump of this embodiment will be described. In the pump 1 of this embodiment, the stretch film 222 of the diaphragm member 22 is stretched in advance. When the stretch film 222, i.e., an acrylic rubber which is a dielectric elastomer, is used in a pre-stretched state, dielectric breakdown strength per unit film thickness is improved compared to a case where the acrylic rubber is used in an unstretched state. Therefore, with the pump 1 of this embodiment, larger voltage can be applied to the stretch film 222. Thus, a stroke of the pump 1 can be increased.

The stretch film 222 of the diaphragm member 22 is stretched in the radial direction. Therefore, an advantageous effect of the stretch can be sufficiently achieved. That is, the dielectric breakdown strength of the stretch film 222 can be sufficiently improved. It suffices that the stretch film 222 be stretched in the radial direction and fixed when the pump 1 is assembled. Therefore, it is not necessary to subject the stretch film 222 to a stretching process in advance before assembling the pump 1. Thus, assembly of the pump 1 is easy.

The diaphragm member 22 is arranged in a state elastically protruded downward compared to the stretched state (dotted line of FIG. 6 described above). In addition, as shown in FIG. 6 described above, the inclination angle θ of the diaphragm member 22 in the low voltage state with respect to that in the stretched state is set to 45° or greater in a cross section along an axial direction. Therefore, the stretch direction (film expansion direction) of the stretch film 222 and the reciprocal movement direction (vertical direction) intersect at an angle of less than 45°. Thus, the stroke of the pump 1 can be increased in this regard as well.

In the pump 1 of this embodiment, the diaphragm member 22 is separated from the fluid chamber R. Therefore, there is a small chance of the cooling liquid contacting the diaphragm member 22. Thus, there is a small chance of the diaphragm member 22 being degraded by the fluid. Since the diaphragm member 22 is separated from the fluid chamber R, the cooling liquid can be selected without taking the material of the diaphragm member 22 into consideration. Thus, the cooling liquid can be selected from a wide variety of choices. In addition, the material of the diaphragm member 22 can be selected from a wide variety of choices.

In the pump 1 of this embodiment, when the rubber elastic member 21 ascends, the rubber elastic member 21 is driven upward by the diaphragm member 22. In addition, when the rubber elastic member 21 descends, the rubber elastic member 21 is driven downward by the rubber elastic member 21 itself. Therefore, the operation of the rubber elastic member 21 is fast. Thus, it is easy to change the volume of the fluid chamber R, and a flow rate of the cooling liquid per unit time can be increased.

In the pump 1 of this embodiment, the rubber elastic member 21 is arranged as a volume changing member of the present invention. Therefore, by using the elastic deformation of the rubber elastic member 21, the volume of the fluid chamber R can be changed relatively easily and at low cost.

In the pump 1 of this embodiment, the rubber elastic member 21 also serves as a return bias member of the present invention. That is, the rubber elastic member 21 drives itself downward by using elastic resilience inherent to the rubber elastic member 21. Therefore, the number of parts can be reduced compared to a case where the rubber elastic member 21 and the return bias member are respectively arranged individually.

In the pump 1 of this embodiment, the diaphragm member 22 has a larger surface area than the rubber elastic member 21. In view of this, a static spring constant of the rubber elastic member 21 is set to be greater than or equal to a static spring constant of the diaphragm member 22. Therefore, a reciprocal movement length of the fluid chamber R can be shortened.

In the pump 1 of this embodiment, the connection member 23 includes the substantially sphere-shaped sphere member 230 and the concave member 231. A load from the diaphragm member 22 is transmitted to the rubber elastic member 21 via the sphere member 230 and the concave member 231. Therefore, the loss of the load is small. Also, the load can be transmitted smoothly.

In the pump 1 of this embodiment, the accommodating surface of the concave section 231 a of the concave member 231 is triangular pyramid mold-shape. The concave section 231 a and the sphere member 230 contact each other at only three points. Therefore, a sliding resistance in the case where the concave section 231 a and the sphere member 230 relatively slide can be reduced.

In the pump 1 of this embodiment, the diaphragm member 22 includes the insulating film 223 (see FIG. 5 described above). Therefore, even in the high voltage state, insulation between the diaphragm member 22 and the connection member 23 can be ensured. In addition, even if the cooling liquid has leaked from the fluid chamber R, a short circuit between the negative electrode 220 and the positive electrode 221 by the cooling liquid can be controlled.

The diaphragm member 22 is formed by laminating the stretch films 222, the negative electrodes 220, and the positive electrodes 221. Therefore, since the stretch films 222 are laminated, a larger load can be generated correspondingly.

In the pump 1 of this embodiment, the negative electrode 220 and the positive electrode 221 are capable of stretching so as not to restrict the stretching of the stretch film 222. That is, the negative electrode 220 and the positive electrode 221 deform integrally with the stretch film 222. Therefore, a desired stroke can easily be ensured.

The output of the pump 1 is ensured by the stretching force of the diaphragm member 22 and the biasing force of the rubber elastic member 21. When the negative electrode 220 and the positive electrode 221 restrict the stretching of the stretch film 222, part of the stretching force of the stretch film 222 and the biasing force of the rubber elastic member 21 is consumed since the negative electrode 220 and the positive electrode 221 are forcibly stretched together with the stretch film 222. Therefore, the output decreases corresponding to the consumed amount. On the other hand, in the pump 1 of this embodiment, the negative electrode 220 and the positive electrode 221 are capable of stretching in accordance with the stretching of the stretch film 222. That is, the negative electrode 220 and the positive electrode 221 can deform integrally with the stretch film 222. Therefore, the decrease of the output can be suppressed. In the pump 1 of this embodiment, the stretch film 222 is formed of acrylic rubber. Therefore, the stretch film 222 is advantageous regarding dielectric properties and dielectric breakdown.

In the pump 1 of this embodiment, the spacer 202 c is mounted between the position corresponding to the bolt hole 200 d on the lower surface of the end plate body 200 a and the position corresponding to the bolt hole 202 b on the upper surface of the flange 202. Therefore, the end plate body 200 a and the flange 202 can be arranged substantially parallel with each other.

Second Embodiment

The main difference of a diaphragm pump of a second embodiment from the diaphragm pump of the first embodiment is that the rubber elastic member is not arranged. As a further difference, a piston member is provided in the second embodiment.

Configuration of Diaphragm Pump

First, a configuration of the diaphragm pump of this embodiment will be described. FIG. 8 shows a perspective view of the pump of this embodiment. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 3. FIG. 9 shows an exploded perspective view of the pump. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 4. FIG. 10 shows an axial direction (vertical direction) sectional view of the pump in the low voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 6. FIG. 11 shows an axial direction sectional view of the pump in the high voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 7.

As shown in FIGS. 8 to 11, the pump 1 mainly includes a housing member 30, a piston member 31, the diaphragm member 22, and a return spring 33. The return spring 33 is included in the return bias member of the present invention.

The housing member 30 includes an end plate 300, an upper case 301, and a lower case 302. The end plate 300 is formed of polyamide and is disk-shaped. A discharge opening 300 f is formed in a central section of the end plate 300. A discharge cylinder section 300 a is provided to protrude on an upper surface of the central section of the end plate 300. An inner space of the discharge cylinder section 300 a and the discharge opening 300 f are communicated. A total of four bolt holes 300 b are formed in the end plate 300 so as to be apart from each other by 90° in the circumferential direction. A spring seat 300 d is formed on a lower surface of the central section of the end plate 300. The spring seat 300 d is ring rib-shaped. The spring seat 300 d is arranged in a circumference of the discharge opening 300 f.

The upper case 301 is formed of polyamide, and includes a cylinder section 301 a and a flange section 301 b. The cylinder section 301 a is arranged below the end plate 300 with a rubber packing 300 c interposed therebetween. A total of four bolt holes 301 c are formed in an upper end opening wall of the cylinder section 301 a so as to be apart from each other by 90° in the circumferential direction. The bolt holes 301 c of the cylinder section 301 a and the bolt holes 300 b of the end plate 300 face each other in the vertical direction. Bolts 300 e penetrate the bolt holes 300 b and the rubber packing 300 c, and are screwed to the bolt holes 301 c. The end plate 300 is fixed to the cylinder section 301 a, with the rubber packing 300 c interposed therebetween, by the bolts 300 e. A suction opening 301 e is formed in a side wall of the cylinder section 301 a. A suction cylinder section 301 d protrudes in the radial direction from an outer circumference surface of the side wall of the cylinder section 301 a. An inner space of the suction cylinder section 301 d and the suction opening 301 e are connected.

The flange section 301 b is formed so as to extend from a lower end opening of the cylinder section 301 a in the radial direction. A total of four bolt holes 301 f are formed in the flange section 301 b so as to be apart from each other by 90° in the circumferential direction.

The lower case 302 is formed of polyamide, and includes a cup section 302 a and a flange section 302 b. The cup section 302 a is bottomed cylinder-shaped, which is open upward. An upper end opening of the cup section 302 a is arranged to face a lower end opening of the cylinder section 301 a of the upper case 301 in the vertical direction. A diaphragm fixing groove 302 c is provided around an outer circumference surface of the cup section 302 a. The flange section 302 b is formed so as to extend from the outer circumference surface of the cup section 302 a in the radial direction. The flange section 302 b is provided below the diaphragm fixing groove 302 c. A total of four bolt holes 302 d are formed in the flange section 302 b so as to be apart from each other by 90° in the circumferential direction. The bolt holes 302 d of the flange section 302 b and the bolt holes 301 f of the flange section 301 b face each other in the vertical direction. A bolt 302 e penetrates the two bolt holes 301 f and 302 d. A nut 302 f is screwed to a penetrating end (lower end) of the bolt 302 e.

The diaphragm member 22 is fixed to the diaphragm fixing groove 302 c of the cup section 302 a, being tightened by a wire 34 formed of steel. The diaphragm member 22 is mounted to the cup section 302 a in a stretched state where the periphery of the diaphragm member 22 is extended in the radial direction.

The piston member 31 is housed in the housing member 30. The piston member 31 is formed of polyamide, and includes a piston body 310 and a rod section 311. The piston body 310 is cup-shaped which is open upward. A spring seat 310 a is arranged in a central section of an upper surface of a bottom wall of the cup-shaped piston body 310. The spring seat 310 a is ring rib-shaped. Ring grooves 310 b are provided around an outer circumference surface of the piston body 310. The ring grooves 310 b are arranged in two vertically aligned rows. Sliding rings 310 c formed of fluoro-rubber are respectively set around the two rows of the ring grooves 310 b. The fluid chamber R is defined by a lower surface of the end plate 300, an inner circumference surface of the cylinder section 301 a of the upper case 301, and an upper surface of the piston body 310.

The rod section 311 is round bar-shaped. The rod section 311 is provided to protrude downward from a central section of a lower surface of the bottom wall of the piston body 310. A pressure receiving section 311 a is formed at a lower end of the rod section 311. The pressure receiving section 311 a is disk-shaped. A lower surface of the pressure receiving section 311 a is formed of fluoro-rubber, and is in contact with the central section of the upper surface of the diaphragm member 22.

The return spring 33 is formed of steel and is coil-shaped. The return spring 33 is mounted between the spring seat 300 d on the lower surface of the end plate 300 and the spring seat 310 a on the upper surface of the piston body 310. In the low voltage state shown in FIG. 10, the central section of the diaphragm member 22 is elastically deformed, and it projects below. On the other hand, the return spring 33 is subjected to compression deformation compared to a natural state. Therefore, the diaphragm member 22 has an upward biasing force. Also, the return spring 33 has a downward biasing force. As shown in FIG. 10, the inclination angle θ of the diaphragm member 22 in the low voltage state with respect to the diaphragm member 22 in the extended state (shown by a dotted line in FIG. 10) is set to 45° or greater.

Method of Assembling Diaphragm Pump

Next, a method of assembling the diaphragm pump of this embodiment will be briefly described. For the assembly, the end plate 300 is first fixed to the upper case 301 by the bolts 300 e. At this time, the rubber packing 300 c is interposed between the end plate 300 and the upper case 301. In addition, the diaphragm member 22 is fixed to the cup section 302 a of the lower case 302 in the stretched state by the wire 34. Next, the piston member 31 is arranged above the diaphragm member 22. Then, the return spring 33 is mounted between the spring seat 310 a of the piston member 31 and the spring seat 300 d on the lower surface of the end plate 300. Subsequently, the bolt 302 e is penetrated from above the bolt hole 301 f to reach below the bolt hole 302 d. Then, the nut 302 f is screwed to the penetrating end (lower end) of the bolt 302 e. In this manner, the pump 1 of this embodiment is assembled.

Operation of Diaphragm Pump

Next, an operation of the diaphragm pump of this embodiment will be described. As shown in FIG. 10, the switch S is opened in the low voltage state. Therefore, voltage is not applied to the stretch film 222 of the diaphragm member 22 (see FIG. 5 described above). As described above, in the low voltage state, the central section of the diaphragm member 22 is elastically deformed, and it projects below. In addition, the return spring 33 is subjected to compression deformation compared to the natural state. Therefore, the diaphragm member 22 has an upward biasing force. Also, the return spring 33 has a downward biasing force.

Closing the switch S causes the high voltage state, whereby the diaphragm member 22 extends in the film expansion direction. However, the periphery of the diaphragm member 22 is fixed to the diaphragm fixing groove 302 c of the cup section 302 a by the wire 34. Therefore, as shown in FIG. 11, the diaphragm member 22 bends downward due to the biasing force of the return spring 33 and the weight of the piston member 31. In addition, the piston member 31 descends. The return spring 33 extends so as to return to the natural state. When the piston member 31 descends, the volume of the fluid chamber R correspondingly increases. Therefore, the suction side check valve V1 opens (the discharge side check valve V2 is closed), whereby the cooling liquid flows into the fluid chamber R from the ECU cooling circuit C via the suction cylinder section 301 d and the suction opening 301 e.

When the switch S is opened again, the high voltage state is switched to the low voltage state. Therefore, as shown in FIG. 10, the diaphragm member 22 moves back upward. When the diaphragm member 22 ascends, the piston member 31 also ascends. Also, the return spring 33 is pressed by the piston member 31 to be subjected to an upward compression deformation. When the piston member 31 ascends, the volume of the fluid chamber R correspondingly decreases. Therefore, the discharge side check valve V2 opens (the suction side check valve V1 is closed), whereby the cooling liquid flows out to the ECU cooling circuit C from the fluid chamber R via the discharge opening 300 f and the discharge cylinder section 300 a.

Advantageous Effect

Next, an advantageous effect of the diaphragm pump of this embodiment will be described. In the pump 1 of this embodiment, portions having common configurations have similar advantageous effects as those of the diaphragm pump of the first embodiment.

In the pump 1 of this embodiment, the volume of the fluid chamber R is changed by the piston body 310 having high rigidity. Therefore, there is a smaller chance of the member itself (the piston body 310 itself) being deformed compared to a case where the volume of the fluid chamber R is changed by a member having low rigidity. Thus, the volume of the fluid chamber R can easily be changed.

In the pump 1 of this embodiment, the lower surface of the pressure receiving section 311 a of the rod section 311 is formed of fluoro-rubber. That is, the lower surface of the pressure receiving section 311 a is formed of a low friction material. Therefore, a sliding resistance in the case where the pressure receiving section 311 a and the diaphragm member 22 relatively slide can be reduced.

Third Embodiment

The only difference of the diaphragm pump of this embodiment from the diaphragm pump of the second embodiment is in the inner structure of the housing member. Only the difference will be described herein.

Configuration of Diaphragm Pump

First, a configuration of the diaphragm pump of this embodiment will be described. FIG. 12 shows an axial direction (vertical direction) sectional view of the pump of this embodiment in the low voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 10. FIG. 13 shows an axial direction sectional view of the pump in the high voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 11.

As shown in FIGS. 12 and 13, a circular film-shaped rubber elastic member 40 is arranged on an inner circumference surface of the cylinder section 301 a. The fluid chamber R is defined by an upper surface of the rubber elastic member 40, the inner circumference surface of the cylinder section 301 a, and the lower surface of the end plate 300. A fixing hole 400 is formed in a central section of the rubber elastic member 40. A connection member 41 is mounted between the rubber elastic member 40 and the diaphragm member 22. The connection member 41 is formed of polyamide and is dumbbell-shaped. That is, an upper end flange section 410 is formed so as to extend in the radial direction from an upper end of the connection member 41. On the other hand, a lower end flange section 411 is formed so as to extend in the radial direction from a lower end of the connection member 41. The upper end flange section 410 is inserted and fixed in the fixing hole 400 of the rubber elastic member 40. The lower end flange section 411 is in contact with the central section of the upper surface of the diaphragm member 22. By the connection member 41 being mounted between the rubber elastic member 40 and the diaphragm member 22, the central section of the diaphragm member 22 is elastically deformed in a low voltage state shown in FIG. 12, and it projects below. In addition, the central section of the rubber elastic member 40 is elastically deformed, and it projects up. Therefore, the diaphragm member 22 has an upward biasing force. Also, the rubber elastic member 40 has a downward biasing force. As shown in FIG. 12, the inclination angle θ of the diaphragm member 22 in the low voltage state with respect to the diaphragm member 22 in the stretched state (shown by a dotted line in FIG. 12) is set to 45° or greater.

Method of Assembling Diaphragm Pump

Next, a method of assembling the diaphragm pump of this embodiment will be briefly described. For the assembly, the cylinder section 301 a of the upper case 301 and the connection member 41 of the rubber elastic member 40 are first integrated by vulcanization adhesion. Next, the end plate 300 is fixed to the upper case 301 by the bolt 300 e. At this time, the rubber packing 300 c is interposed between the end plate 300 and the upper case 301. In addition, the diaphragm member 22 is fixed to the cup section 302 a of the lower case 302 in the stretched state by the wire 34. Then, the bolt 302 e is penetrated from above the bolt hole 301 f to reach below the bolt hole 302 d. Then, the nut 302 f is screwed to the penetrating end (lower end) of the bolt 302 e. In this manner, the pump 1 of this embodiment is assembled.

Operation of Diaphragm Pump

Next, an operation of the diaphragm pump of this embodiment will be described. As shown in FIG. 12, the switch S is opened in the low voltage state. Therefore, voltage is not applied to the stretch film 222 of the diaphragm member 22 (see FIG. 5 described above). As described above, in the low voltage state, the central section of the diaphragm member 22 is elastically deformed, and it projects below. Therefore, the diaphragm member 22 has an upward biasing force. Also, the central section of the rubber elastic member 40 is elastically deformed, and it projects up. Therefore, the rubber elastic member 40 has a downward biasing force.

Closing the switch S causes the high voltage state, whereby the diaphragm member 22 extends in the film expansion direction. However, the periphery of the diaphragm member 22 is fixed to the diaphragm fixing groove 302 c of the cup section 302 a by the wire 34. Therefore, as shown in FIG. 13, the diaphragm member 22 bends downward due to the biasing force of the rubber elastic member 40 and the weight of the piston member 31. In addition, the connection member 41 descends. The rubber elastic member 40 moves back to a natural state. When the rubber elastic member 40 moves back, the volume of the fluid chamber R correspondingly increases. Therefore, the suction side check valve V1 opens (the discharge side check valve V2 is closed), whereby the cooling liquid flows into the fluid chamber R from the ECU cooling circuit C via the suction cylinder section 301 d and the suction opening 301 e.

When the switch S is opened again, the high voltage state is switched to the low voltage state. Therefore, as shown in FIG. 12, the diaphragm member 22 moves back upward. When the diaphragm member 22 ascends, the central section of the rubber elastic member 40 elastically protrudes upward. When the central section of the rubber elastic member 40 protrudes upward, the volume of the fluid chamber R correspondingly decreases. Therefore, the discharge side check valve V2 opens (the suction side check valve V1 is closed), whereby the cooling liquid flows out to the ECU cooling circuit C from the fluid chamber R via the discharge opening 300 f and the discharge cylinder section 300 a.

Advantageous Effect

Next, an advantageous effect of the diaphragm pump of this embodiment will be described. In the pump 1 of this embodiment, portions having common configurations have similar advantageous effects as those of the diaphragm pump of the first embodiment. In the pump 1 of this embodiment, the inner structure of the housing member 30 is simplified. In addition, the number of parts is small. Therefore, an assembly work becomes easy.

Fourth Embodiment

The only difference of the diaphragm pump of a fourth embodiment from the diaphragm pump of the second embodiment is in the inner structure of the housing member. Only the difference will be described herein.

Configuration of Diaphragm Pump

First, a configuration of the diaphragm pump of this embodiment will be described. FIG. 14 shows an exploded perspective view of the pump of this embodiment. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 9. FIG. 15 shows an axial direction (vertical direction) sectional view of the pump in the low voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 10. FIG. 16 shows an axial direction sectional view of the pump in the high voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 11.

As shown in FIGS. 14 to 16, a step section 301 g is formed in an inner periphery of the flange section 301 b of the upper case 301. The step section 301 g is provided with a spring seat plate 50. The spring seat plate 50 is formed of polyamide and is disk-shaped. A rod insertion hole 500 is formed in a central section of the spring seat plate 50.

The piston member 51 includes a piston body 510 and a rod section 511. The piston body 510 and the rod section 511 are separate parts. The piston body 510 is formed of polyamide, and is cup-shaped which is open upward. A rod fixing hole 510 d is formed in a central section of a lower surface of a bottom wall of the piston body 510. Ring grooves 510 b are provided around an outer circumference surface of the piston body 510. The ring grooves 510 b are arranged in two vertically aligned rows. Sliding rings 510 c formed of fluoro-rubber are respectively set around the two rows of the ring grooves 510 b. The fluid chamber R is defined by a lower surface of the end plate 300, an inner circumference surface of the cylinder section 301 a of the upper case 301, and an upper surface of the piston body 510.

The rod section 511 is formed of polyamide and is round bar-shaped. The rod section 511 is inserted in the rod insertion hole 500 of the spring seat plate 50. An upper end of the rod section 511 is screwed to the rod fixing hole 510 d of the piston body 510. A pressure receiving section 511 a is formed at a lower end of the rod section 511. The pressure receiving section 511 a is disk-shaped. A lower surface of the pressure receiving section 511 a is formed of fluoro-rubber. The lower surface of the pressure receiving section 511 a is in contact with the central section of the upper surface of the diaphragm member 22.

The return spring 53 is formed of steel and is coil-shaped. The return spring 53 is included in the return bias member of the present invention. The return spring 53 is provided around the rod section 511. The return spring 53 is mounted between a lower surface of the spring seat plate 50 and an upper surface of the pressure receiving section 511 a at the lower end of the rod section 511. In the low voltage state shown in FIG. 15, the central section of the diaphragm member 22 is elastically deformed, and it projects below. On the other hand, the return spring 53 is subjected to compression deformation compared to a natural state. Therefore, the diaphragm member 22 has an upward biasing force. Also, the return spring 53 has a downward biasing force. As shown in FIG. 15, the inclination angle θ of the diaphragm member 22 in the low voltage state with respect to the diaphragm member 22 in the stretched state (shown by a dotted line in FIG. 15) is set to 45° or greater.

Method of Assembling Diaphragm Pump

Next, a method of assembling the diaphragm pump of this embodiment will be briefly described. For the assembly, the end plate 300 is first fixed to the upper case 301 by the bolts 300 e. At this time, the rubber packing 300 c is interposed between the end plate 300 and the upper case 301. In addition, the diaphragm member 22 is fixed to the cup section 302 a of the lower case 302 in the stretched state by the wire 34. Next, the rod section 511 is inserted in the rod insertion hole 500 of the spring seat plate 50. At this time, the return spring 53 is mounted between the spring seat plate 50 and the pressure receiving section 511 a. Then, the piston body 510 is screwed to the upper end of the rod section 511. Then, an assembled body of the piston member 51, the spring seat plate 50, and the return spring 53 is arranged above the central section of the diaphragm member 22. Then, the bolt 302 e is penetrated from above the bolt hole 301 f to reach below the bolt hole 302 d. At this time, the periphery of the spring seat plate 50 is inserted in the step section 301 g. Then, the nut 302 f is screwed to the penetrating end of the bolt 302 e. In this manner, the pump 1 of this embodiment is assembled.

Operation of Diaphragm Pump

Next, an operation of the diaphragm pump of this embodiment will be described. As shown in FIG. 15, the switch S is opened in the low voltage state. Therefore, voltage is not applied to the stretch film 222 of the diaphragm member 22 (see FIG. 5 described above). As described above, in the low voltage state, the central section of the diaphragm member 22 is elastically deformed, and it projects below. On the other hand, the return spring 53 is subjected to compression deformation compared to a natural state. Therefore, the diaphragm member 22 has an upward biasing force, and the return spring 53 has a downward biasing force.

Closing the switch S causes the high voltage state, whereby the diaphragm member 22 extends in the film expansion direction. However, the periphery of the diaphragm member 22 is fixed to the diaphragm fixing groove 302 c of the cup section 302 a by the wire 34. Therefore, as shown in FIG. 16, the diaphragm member 22 bends downward due to the biasing force of the return spring 53 and the weight of the piston member 51. In addition, the piston member 51 also descends. When the piston member 51 descends, an interval between the spring seat plate 50 and the pressure receiving section 511 a increases. Therefore, the return spring 53 mounted between the two members extends so as to return to the natural state. When the piston member 51 descends, the volume of the fluid chamber R correspondingly increases. Therefore, the suction side check valve V1 opens (the discharge side check valve V2 is closed), whereby the cooling liquid flows into the fluid chamber R from the ECU cooling circuit C via the suction cylinder section 301 d and the suction opening 301 e.

When the switch S is opened again, the high voltage state is switched to the low voltage state. Therefore, as shown in FIG. 15, the diaphragm member 22 moves back upward. When the diaphragm member 22 ascends, the piston member 51 also ascends. When the piston member 51 ascends, the interval between the spring seat plate 50 and the pressure receiving section 511 a decreases. Therefore, the return spring 53 mounted between the two members is subjected to compression deformation. When the piston member 51 ascends, the volume of the fluid chamber R correspondingly decreases. Therefore, the discharge side check valve V2 opens (the suction side check valve V1 is closed), whereby the cooling liquid flows out to the ECU cooling circuit C from the fluid chamber R via the discharge opening 300 f and the discharge cylinder section 300 a.

Advantageous Effect

Next, an advantageous effect of the diaphragm pump of this embodiment will be described. In the pump 1 of this embodiment, portions having common configurations have similar advantageous effects as those of the diaphragm pump of the first embodiment.

In the pump 1 of this embodiment, the volume of the fluid chamber R is changed by the piston body 510 having high rigidity. Therefore, there is a smaller chance of the member itself (the piston body 510 itself) being deformed compared to a case where the volume of the fluid chamber R is changed by a member having low rigidity. Thus, the volume of the fluid chamber R can easily be changed.

In the pump 1 of this embodiment, the lower surface of the pressure receiving section 511 a of the rod section 511 is formed of fluoro-rubber. That is, the lower surface of the pressure receiving section 511 a is formed of a low friction material. Therefore, a sliding resistance in the case where the pressure receiving section 511 a and the diaphragm member 22 relatively slide can be reduced.

In the pump 1 of this embodiment, the return spring 53 is arranged separate from the fluid chamber R. Therefore, the return spring 53 hardly contacts the cooling liquid. Thus, there is a small chance of the return spring 53 being degraded by the cooling liquid. Since there is small necessity of taking a resistance to fluid of the return spring 53 into consideration, the material of the return spring 53 can be selected from a wide variety of choices.

In the pump 1 of this embodiment, the fluid chamber R is not provided with the return spring 53. Therefore, there is no chance of the return spring 53 acting as a flow resistance to the cooling liquid during suction or discharge. Thus, the fluidity of the cooling liquid is high.

In the pump 1 of this embodiment, the spring seat plate 50 is mounted between the fluid chamber R and the diaphragm member 22. Therefore, even if the cooling liquid leaks from the fluid chamber R, the diaphragm member 22 is hardly exposed to the cooling liquid. Thus, the diaphragm member 22 is unlikely to cause a short circuit.

Fifth Embodiment

The main difference of a diaphragm pump of a fifth embodiment from the diaphragm pump of the first embodiment is that the inner structure of the housing member is simple. As a further difference, the low voltage state and the high voltage state respectively correspond to a suction process of the cooling liquid and a discharge process of the cooling liquid in the fifth embodiment.

Configuration of Diaphragm Pump

First, a configuration of the diaphragm pump of this embodiment will be described. FIG. 17 shows a perspective view of the pump of this embodiment. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 3. FIG. 18 shows an exploded perspective view of the pump. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 4. FIG. 19 shows an axial direction (vertical direction) sectional view of the pump in the low voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 6. FIG. 20 shows an axial direction sectional view of the pump in the high voltage state. Note that corresponding portions will be denoted by the same reference symbols as those of FIG. 7.

As shown in FIGS. 17 to 20, the pump 1 mainly includes a housing member 60, a rubber elastic member 61 (shown by grid lines in FIG. 18 for convenience of illustration), the diaphragm member 22, and a connection member 63.

The housing member 60 includes an upper end plate 600, a lower end plate 601, and an intermediate cylinder member 602. The upper end plate 600 is formed of polyamide and is disk-shaped. A suction opening 600 a and a discharge opening 600 b are formed in the upper end plate 600. A suction cylinder section 600 c is provided to protrude in the circumference of the suction opening 600 a on an upper surface of the upper end plate 600. A discharge cylinder section 600 d is provided to protrude in the circumference of the discharge opening 600 b on the upper surface of the upper end plate 600. A total of four bolt holes 600 e are formed in the upper end plate 600 so as to be apart from each other by 90° in the circumferential direction. The lower end plate 601 is formed of polyamide and is disk-shaped. A total of four bolt holes 601 a are formed in the lower end plate 601 so as to be apart from each other by 90° in the circumferential direction.

The intermediate cylinder member 602 is formed of polyamide and is cylinder-shaped. The intermediate cylinder member 602 is mounted between the upper end plate 600 and the lower end plate 601. A rubber elastic member fixing groove 602 a is provided around the vicinity of an upper end of an outer circumference surface of the intermediate cylinder member 602. An upper flange section 602 b is formed below the rubber elastic member fixing groove 602 a. The upper flange section 602 b is formed so as to extend from the outer circumference surface of the intermediate cylinder member 602 in the radial direction. A total of four bolt holes 602 c are formed in the upper flange section 602 b so as to be apart from each other by 90° in the circumferential direction. The bolt holes 602 c of the upper flange section 602 b and the bolt holes 600 e of the upper end plate 600 face each other in the vertical direction. A bolt 602 d penetrates the bolt holes 600 e and 602 c. By a nut 602 e being screwed to a penetrating end (lower end) of the bolt 602 d, the upper end plate 600 is fixed to an upper end of the intermediate cylinder member 602 in a state where the rubber elastic member 61 described later is sandwiched.

On the other hand, a diaphragm fixing groove 602 f is provided around the vicinity of a lower end of the outer circumference surface of the intermediate cylinder member 602. A lower flange section 602 g is formed above the diaphragm fixing groove 602 f. The lower flange section 602 g is formed so as to extend from the outer circumference surface of the intermediate cylinder member 602 in the radial direction. A total of four bolt holes 602 h are formed in the lower flange section 602 g so as to be apart from each other by 90° in the circumferential direction. The bolt holes 602 h of the lower flange section 602 g and the bolt holes 601 a of the lower end plate 601 face each other in the vertical direction. A bolt 602 k penetrates the bolt holes 601 a and 602 h. By a nut 602 m being screwed to a penetrating end (upper end) of the bolt 602 k, the lower end plate 601 is fixed to a lower end of the intermediate cylinder member 602 in a state where the diaphragm member 22 described later is sandwiched.

The rubber elastic member 61 is circular film-shaped. The rubber elastic member 61 covers an upper end opening of the intermediate cylinder member 602. The rubber elastic member 61 is fixed to the rubber elastic member fixing groove 602 a by being tightened by a wire 64 formed of steel.

The diaphragm member 22 is circular film-shaped. The diaphragm member 22 covers a lower end opening of the intermediate cylinder member 602. The diaphragm member 22 is fixed to the diaphragm fixing groove 602 f by being tightened by a wire 65 formed of steel. The diaphragm member 22 is mounted in a stretched state where the periphery thereof is extended in the radial direction. The central section of the upper surface of the diaphragm member 22 and a central section of a lower surface of the rubber elastic member 61 are bonded. Therefore, the central section of the diaphragm member 22 is elastically deformed to protrude upward. In addition, the central section of the rubber elastic member 61 is elastically deformed to protrude downward.

The connection member 63 includes an upper connection piece 630 and a lower connection piece 631. The upper connection piece 630 is formed of polyamide and is disk-shaped. The upper connection piece 630 is arranged in the central section of the upper surface of the rubber elastic member 61. A total of four bolt holes 630 a are formed in the upper connection piece 630 so as to be apart from each other by 90° in the circumferential direction.

The lower connection piece 631 is formed of polyamide and is disk-shaped. The lower connection piece 631 is arranged in the central section of the lower surface of the diaphragm member 22. A total of four bolt holes 631 a are formed in the lower connection piece 631 so as to be apart from each other by 90° in the circumferential direction. The bolt holes 631 a of the lower connection piece 631 and the bolt holes 630 a of the upper connection piece 630 face each other in the vertical direction.

A bolt 632 penetrates the bolt hole 630 a, the rubber elastic member 61, the diaphragm member 22, and the bolt hole 631 a. By a nut 633 being screwed to a penetrating end (lower end) of the bolt 632, the upper connection piece 630 and the lower connection piece 631 are assembled in a state where the rubber elastic member 61 and the diaphragm member 22 are sandwiched. The fluid chamber R is defined by the upper surface of the rubber elastic member 61 protruding downward and the lower surface of the upper end plate 600.

In the low voltage state shown in FIG. 19, the central section of the diaphragm member 22 is elastically deformed, and it projects up. On the other hand, the central section of the rubber elastic member 61 is elastically deformed, and it projects below. Therefore, the diaphragm member 22 has a downward biasing force. Also, the rubber elastic member 61 has an upward biasing force. As shown in FIG. 19, the inclination angle θ of the diaphragm member 22 in the low voltage state with respect to the diaphragm member 22 in the stretched state (shown by a dotted line in FIG. 19) is set to 45° or greater.

Method of Assembling Diaphragm Pump

Next, a method of assembling the diaphragm pump of this embodiment will be briefly described. For the assembly, the central section of the lower surface of the rubber elastic member 61 and the central section of the upper surface of the diaphragm member 22 are first bonded. Next, the central section of the rubber elastic member 61 and the central section of the diaphragm member 22 are sandwiched and fixed by the connection member 63. Then, the rubber elastic member 61 is fixed to the rubber elastic member fixing groove 602 a of the intermediate cylinder member 602 using the wire 64. In addition, the diaphragm member 22 is fixed to the diaphragm fixing groove 602 f of the intermediate cylinder member 602 by the wire 65. Note that the diaphragm member 22 is fixed in the stretched state. Then, the upper end plate 600 is fixed to an upper end opening of the intermediate cylinder member 602 using the bolts 602 d and the nuts 602 e while the periphery of the rubber elastic member 61 is being sandwiched. In addition, the lower end plate 601 is fixed to the lower end opening of the intermediate cylinder member 602 using the bolts 602 k and the nuts 602 m while the periphery of the diaphragm member 22 is being sandwiched. In this manner, the pump 1 of this embodiment is assembled.

Operation of Diaphragm Pump

Next, an operation of the diaphragm pump of this embodiment will be described. As shown in FIG. 19, the switch S is opened in the low voltage state. Therefore, voltage is not applied to the stretch film 222 of the diaphragm member 22 (see FIG. 5 described above). As described above, in the low voltage state, the central section of the diaphragm member 22 is elastically deformed, and it projects up. Therefore, the diaphragm member 22 has a downward biasing force. On the other hand, the central section of the rubber elastic member 61 is elastically deformed, and it projects below. Therefore, the rubber elastic member 61 has an upward biasing force.

Closing the switch S causes the high voltage state, whereby the diaphragm member 22 extends in the film expansion direction. However, the periphery of the diaphragm member 22 is fixed to the diaphragm fixing groove 602 f of the intermediate cylinder member 602 by the wire 65. Therefore, as shown in FIG. 20, the diaphragm member 22 is pulled by the biasing force of the rubber elastic member 61 to bend upward. In addition, the central section of the rubber elastic member 61 is subjected to an upward shrinkage deformation. When the rubber elastic member 61 is subjected to the shrinkage deformation, the volume of the fluid chamber R correspondingly decreases. Therefore, the discharge side check valve V2 opens (the suction side check valve V1 is closed), whereby the cooling liquid flows out to the ECU cooling circuit C from the fluid chamber R via the discharge opening 300 f and the discharge cylinder section 300 a.

When the switch S is opened again, the high voltage state is switched to the low voltage state. Therefore, as shown in FIG. 19, the diaphragm member 22 moves back downward against the biasing force of the rubber elastic member 61. When the diaphragm member 22 descends, the central section of the rubber elastic member 61 is pulled by the diaphragm member 22 to protrude downward. Therefore, the volume of the fluid chamber R increases. When the volume of the fluid chamber R increases, the suction side check valve V1 opens (the discharge side check valve V2 is closed), whereby the cooling liquid flows into the fluid chamber R from the ECU cooling circuit C via the suction cylinder section 301 d and the suction opening 301 e.

Advantageous Effect

Next, an advantageous effect of the diaphragm pump of this embodiment will be described. In the pump 1 of this embodiment, portions having common configurations have similar advantageous effects as those of the diaphragm pump of the first embodiment.

In the pump 1 of this embodiment, the inner structure of the housing member 60 is simple. Therefore, assembling is easy. Also, the pump 1 can easily be reduced in size. In the pump 1 of this embodiment, the intermediate cylinder member 602 has a vertically symmetrical shape. Therefore, there is no need to pay attention to the vertical direction of the intermediate cylinder member 602 when mounting the rubber elastic member 61 or the diaphragm member 22 to the intermediate cylinder member 602. Therefore, assembly is easy in this regard as well.

Others

Embodiments of the diaphragm pump of the present invention have been described above. However, embodiments are not particularly limited to the embodiments described above. The present invention may be carried out through various modified embodiments or improved embodiments possible to those skilled in the art.

In the embodiments described above, the housing members 20, 30, 60, and the like are formed of polyamide, but the material is not particularly limited. For example, the housing members 20, 30, 60, and the like may be formed of other resin or metal. In the embodiments described above, the return spring 33 or 53 is used as the return bias member, but other types of springs, e.g., plate spring, disk spring, and the like, may also be used. A return bias member formed of rubber, elastomer, or the like may also be used.

In the embodiments described above, the diaphragm member 22 is fixed using the clamp ring 224 or the wire 34 or 65, but the diaphragm member 22 may also be fixed by other methods such as bonding.

In the embodiments described above, one of the suction openings 200 f, 301 e, and 600 a and one of the discharge openings 200 g, 300 f, and 600 b are respectively arranged to the single pump 1, but the numbers of the arranged suction openings and the discharge openings are not particularly limited.

In the embodiments described above, the pump 1 of the present invention is used for the cooling liquid of the ECU cooling circuit C, but the application of the pump 1 is not particularly limited. For example, the pump 1 may be used for pumping various fluids such as fuel, oil, and water.

In the embodiments described above, the lower surface of the pressure receiving section 311 a of the rod section 311 is formed of fluoro-rubber which is a low friction material. However, the lower surface of the pressure receiving section 311 a may also be formed of other low friction materials such as fluororesin, silicon resin, and diamond-like carbon (DLC). Low friction materials such as lubricating oil and fine particles may also be used. The number of laminated layers of the negative electrodes 220, the positive electrodes 221, and the stretch films 222 of the diaphragm member 22 is also not particularly limited. In the embodiments described above, bolts and nuts are mainly used for the assembly of the housing members 20, 30, and 60, but the housing members 20, 30, and 60 may also be assembled by bonding, welding, claw engagement, or the like. In the first embodiment described above, the accommodating surface of the concave section 231 a is triangular pyramid mold-shaped, but the accommodating surface of the concave section 231 a may also be, for example, sphere mold-shaped to fit the surface of a sphere, quadrangular pyramid mold-shaped to fit the surface of a quadrangular pyramid, or the like. 

1. A diaphragm pump comprising: a housing member including a fluid chamber, a suction opening which sucks a fluid into the fluid chamber, and a discharge opening which discharges the fluid from the fluid chamber; a volume changing member which changes a volume of the fluid chamber; a diaphragm member which is fixed to the housing member in a stretched state where a periphery of the diaphragm member is extended in a radial direction, and which is arranged separate from the fluid chamber, the diaphragm member including a pair of electrodes and a stretch film formed of dielectric elastomer, which is provided between the pair of electrodes and an extension amount of which increases in a film expansion direction as an applied voltage between the pair of electrodes increases, and the diaphragm member driving the volume changing member in a forward movement direction which intersects with the film expansion direction; a return bias member which drives the volume changing member in a backward movement direction opposite to the forward movement direction; and a connection member which connects the diaphragm member and the volume changing member so as to be capable of power transmission; wherein a low voltage state where the applied voltage between the pair of electrodes is low and a high voltage state where the applied voltage between the pair of electrodes is high can be switched; and wherein, in the low voltage state, the diaphragm member and the return bias member have an accumulated driving force with respect to the volume changing member, the diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to the diaphragm member in the stretched state is set to 45° or greater in a cross section in a reciprocal movement direction.
 2. The diaphragm pump according to claim 1, wherein the volume changing member is a rubber elastic member.
 3. The diaphragm pump according to claim 2, wherein the rubber elastic member also serves as the return bias member.
 4. The diaphragm pump according to claim 2, wherein a static spring constant of the rubber elastic member is set to be greater than or equal to a static spring constant of the diaphragm member.
 5. The diaphragm pump according to claim 1, further comprising: a piston member including a piston body which serves as the volume changing member and a rod section which serves as the connection member connected with the piston body.
 6. The diaphragm pump according to claim 1, wherein the connection member includes a substantially spherical surface-shaped spherical surface section contacting the diaphragm member.
 7. The diaphragm pump according to claim 6, wherein the connection member includes a substantially sphere-shaped sphere member which includes the spherical surface section, and a concave member which contacts the volume changing member and includes a concave section accommodating a part of the sphere member.
 8. The diaphragm pump according to claim 7, wherein an accommodating surface of the concave section has a triangular pyramid mold shape which fits a surface of a triangular pyramid so that the sphere member comes into contact with the accommodating surface of the concave section at three points.
 9. The diaphragm pump according to claim 1, wherein at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of a low friction material.
 10. The diaphragm pump according to claim 1, wherein at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of an insulating material.
 11. The diaphragm pump according to claim 1, wherein a surface of the diaphragm member on a side of the fluid chamber is formed of an insulating material.
 12. The diaphragm pump according to claim 1, wherein the diaphragm member is formed of a plurality of the stretch films being laminated with the electrode interposed therebetween.
 13. The diaphragm pump according to claim 1, wherein the electrode is capable of stretching so as not to restrict stretching of the stretch film.
 14. The diaphragm pump according to claim 1, wherein the dielectric elastomer is one or more selected from a group consisting of acrylic rubber, silicone rubber, fluoro-rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, styrene butadiene rubber, and natural rubber. 